title: Direct comparison between two quantitative assays in the measurement of maternal anti-HPA-1a antibody in neonatal alloimmune thrombocytopenia (NAIT).
abstract: BACKGROUND
  Around 80% of severe neonatal alloimmune thrombocytopenia (NAIT) cases in the Caucasian population are due to anti-HPA-1a antibodies. However, the relationship between anti-HPA-1a antibody quantity and severity of NAIT has been subject to debate, possibly due to discrepant results between studies incorporating different assays (such as ELISA and MAIPA) and the number of samples. The aim of this study was to compare the level of maternal anti-HPA-1a antibodies in the same samples, using two different methods; quantitative ELISA and quantitative MAIPA. At the same time, the relationship between the maternal anti-HPA-1a antibody quantity and the newborn platelet count was examined.
  
  
  METHODS
  Plasma samples were obtained from HPA-1a negative mothers giving birth to children with different platelet counts (i.e. NAIT vs normal platelet count). The antibody levels were quantified blindly in the respective assays using standards calibrated against the international standard NIBSC 03/152.
  
  
  RESULTS
  A linear correlation was observed between quantitative MAIPA and quantitative ELISA results. However, there were many individual variations giving a mean ratio of disagreement between the quantitative ELISA and quantitative MAIPA of 2.84. Furthermore, regression analysis revealed a significant relation between anti-HPA-1a antibody quantity measured by MAIPA, but not ELISA, and the newborn platelet count.
  
  
  CONCLUSIONS
  The results indicate that differences observed between various studies with regard to NAIT severity and anti-HPA-1a quantity could partly be due to different assays used.
authors.affiliation: Scottish National Blood Transfusion Service (SNBTS) R&D Directorate, Edinburgh and Aberdeen, National Science Laboratory, 21 Ellen's Glen Road, Edinburgh EH17 7QT, Scotland. hagop.bessos@snbts.csa.scot.nhs.uk
authors.forename: Hagop
authors.initials: H
authors.lastname: Bessos
authors.forename: Mette K
authors.initials: MK
authors.lastname: Killie
authors.forename: Maryana
authors.initials: M
authors.lastname: Matviyenko
authors.forename: Anne
authors.initials: A
authors.lastname: Husebekk
authors.forename: Stan J
authors.initials: SJ
authors.lastname: Urbaniak
mesh_terms: D016824:Antigens, Human Platelet; D001323:Autoantibodies / Q000097:blood*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D054098:Thrombocytopenia, Neonatal Alloimmune / Q000097:blood*
chemical_list: D016824:Antigens, Human Platelet; D001323:Autoantibodies; C083451:human platelet antigen 1b